1. Technical Field of the Invention
The invention relates to an imaging device for use in nuclear magnetic resonance (NMR) using coils that serve for the transmission and/or reception of the frequency signals (Larmor frequency) and which are assembled in fields (arrays), the individual coil comprising a conductor track, which defines an area.
2. Description of the Prior Art
Nuclear magnetic resonance has found widespread use as an important imaging process. Therein, the effect is utilized that atoms in a homogeneous magnetic field, when supplied with energy by means of electromagnetic waves of particular frequencies, undergo excitation by virtue of the absorption. The frequency here is determined from the intensity of the constant magnetic field and the special characteristic properties of the nucleus. After a short time, the excited spin returns to its ground state, that is to say to the lowest energy state, and emits an electromagnetic signal, which is received by means of receiving coils and is utilized to construct the image. In principle, the same coil elements can be used for excitation (transmitting a signal), as well as for reception. To this end, a relatively large number of coils are assembled in so-called arrays. The greater the density, that is to say the number of individual coils per unit area, the better is the signal/noise ratio. Thereby, e.g., the resolution of the image derived can be increased. A decisive advantage is further the possibility of using parallel imaging processes, which make a higher recording rate feasible.
From the prior art (see, for example, WO 02/315 22), so-called MTL (microstrip transmission line) coils are known, which in their simplest configuration consist of a strip-shaped conductor, which is applied to a dielectric and on the opposite side of which a conductive base plate is disposed.